The present invention relates to a terminal base for an I/O unit, and particularly relates to such a terminal base for an I/O unit which is intended to be connected with a central processing unit of a computer system. Even more particularly, the present invention relates to such a terminal base for an I/O unit which is intended to be connected with a central processing unit of a computer system for processing inputs and outputs of said central processing unit, which particularly makes easy the work of installation and connection while retaining the virtues of easy servicability and manufacturing and assembly efficiency.
In the prior art, there have been proposed various types of I/O unit for use with central processing units of computer systems. Such an I/O unit, when used for output from the central processing unit, is tupically used for amplifying one or more outputs from said central processing unit by receiving said output or outputs and using it or them to switch one or more relays, the resulting signal or signals outputted from the relay or relays then being transmitted to the outside. On the other hand, when used for input to the central processing unit, such an I/O unit is typically used for amplifying one or more inputs to said central processing unit by receiving said input or inputs and using it or them to switch one or more relays, the resulting signal or signals outputted from the relay or relays, which is a TTL (transistor-transistor-logic) signal then being transmitted to the central processing unit. Two prior art types of such I/O units will now be explained with regard to FIGS. 1 and 2 of the appended drawings, which are schematic perspective partly phantom views of said prior art type I/O units.
First, referring to FIG. 1, this first conventional type of I/O unit, denoted as 31, comprises a CPU (central processing unit) 32, which receives inputs and which produces outputs. A rack 33 is provided within the I/O unit 31, and in this rack 33 there are slotted a plurality of printed circuit boards 34. A terminal base 36 is also provided as fitted within the I/O unit 31. On each of the printed circuit boards 34 there are mounted one or more of a plurality of relay units 35, and a first plurality of wires 41 connects the CPU 32 to the rack 33 and to the printed circuit boards 34 therein, while a second plurality of wires 42 connects the rack 33 and the printed circuit boards 34 therein to the terminal base 36. And a third plurality of wires 43, extending from devices exterior to this I/O unit 31 and not particularly shown, is connected to the terminal base 36. Thus, a typical output from the CPU 32 is transmitted via one or more of the plurality of wires 41 to the rack 33 and to an appropriate one or more of the relays 35 mounted on the printed circuit boards 34 fitted in said rack 33, and actuates said one or more of said relays 35 to produce an amplified output signal which is then fed to the wires 43 on the outside via one or more of the plurality of wires 42 and via the terminal base 36. Similarly, a typical input for being fed to the CPU 32 is transmitted from the outside through the wires 43 to one or more of the plurality of wires 42 via the terminal base 36, and then is fed to an appropriate one or more of the relays 35 mounted on the printed circuit boards 34 fitted in the rack 33, and is converted into (for example) a TTL level signal, which is then fed via one or more of the plurality of wires 41 to the CPU 32.
Further, referring to FIG. 2, a second conventional type of I/O unit, also denoted as 31, similarly comprises a CPU (central processing unit) 32, which similarly receives inputs and which produces outputs. A socket 37 is provided within the I/O unit 31, and in this socket 37 there are fitted a plurality of relay units 35. A terminal base 36 is also provided as fitted within the I/O unit 31. A first plurality of wires 41 connects the CPU 32 to the socket 37 and to the relay units 35 fitted therein, while a second plurality of wires 42 connects the socket 37 and the relay units 35 fitted therein to the terminal base 36. And a third plurality of wires 43, extending from devices exterior to this I/O unit 31 and not particularly shown, is connected to the terminal base 36. Thus, a typical output from the CPU 32 is transmitted via. one or more of the plurality of wires 41 to the socket 37 and to an appropriate one or more of the relays 35 fitted in said socket 37, and actuates said one or more of said relays 35 to produce an amplified output signal which is then fed to the wires 43 on the outside via one or more of the plurality of wires 42 and via the terminal base 36. Similarly, a typical input for being fed to the CPU 32 is transmitted from the outside through the wires 43 to one or more of the plurality of wires 42 via the terminal base 36, and then if fed to an appropriate one or more of the relays 35 fitted in the socket 37, and is converted into (for example) a TTL level signal, which is then fed via one or more of the plurality of wires 41 to the CPU 32.
However, the I/O unit of the first type shown in FIG. 1 is subject to the problems that, since all of the relay units 35 are mounted on the printed circuit boards 34, the replacement of any ones of said relay units 35 which may be faulty is not easy, and further the diagnosis of which one or ones of said relay units 35 which actually is faulty is relatively difficult. Thus, the efficiency of maintenance of this first type I/O unit is relatively low. Further, much wiring is required to be provided inside the casing of this I/O unit 31, and accordingly the efficiency of manufacture and of assembly of this I/O unit 31 is relatively low.
On the other hand, in the case of the I/O unit of the second type shown in FIG. 2, it is true that the replacement of any ones of said relay units 35 which may be faulty is easier than in the case of the FIG. 1 type of I/O unit, and further it is true that the diagnosis of which one or ones of said relay units 35 which actually is faulty is easier than in the case of said FIG. 1 type of I/O unit. Accordingly, this second type of I/O unit is more advantageous as regards efficiency of maintenance than is the first type of I/O unit. However, since also in this second type of I/O unit still a double set of wiring is required to be provided inside its casing--i.e., both the plurality of wires 41 between the CPU 32 and the socket 37 and also the plurality of wires 41 between the socket 37 and the terminal base 36 are required to be provided--accordingly the efficiency of manufacture and of assembly of this second type of I/O unit are no better than the efficiency of manufacture and of assembly of the first type of I/O unit shown in FIG. 1 and described above.